1. Field of the Invention
The present invention relates to ankle prostheses.
2. Brief Description of the Related Art
Numerous prostheses were put forth that comprise a tibial and a talar element, each provided with an articular surface; these articular surfaces are shaped in such a manner that, by interacting as a whole, they provide the necessary articulation between the foot and the leg. Several shapes of articular surfaces were contemplated, some of which were spherical while others were constituted by surfaces of revolution around an axis essentially perpendicular to the tibial axis, allowing a rotary motion only around this one axis. Furthermore, one or the other of the tibial and talar elements can be provided with a plane interface, which allows a sliding between two elements, one of which is secured to the bone while the other one delimits the articular surface.
It must be noted, however, that in all the various currently used prostheses the obtained movement of the articulation does not correspond to the natural articular movement of the ankle, a fact that manifests itself in an inadequacy between the movement allowed by the articular surfaces and the movement the various ligaments tend to impose upon the foot. This inadequacy is evidenced by the appearance of limitations and stresses on the prosthesis which, in turn, can give rise to wear and tear, a loss of mobility or even a loosening of the prosthesis. Furthermore, it can cause discomfort and unpleasant pains to the patient.